Greenalleycat
Structural
- Jul 12, 2021
- 513
Howdy all,
My boss and I just went down a rabbit hole that ultimately neither of us know the answer to.
Imagine a building over deep, stiff concrete piles that transfer loads to bedrock say 25m below ground level (the numbers don't matter, this is an academic discussion primarily)
Presumably the soil layers between bedrock and ground will vary with depth, some topsoil then maybe various soft and hard sands, clays, or silts - whatever it is
The soil layers will presumably have differing mass, stiffness, and depth per layer, and so under earthquake shaking will respond uniquely to each layer
This is conceptually similar to a multi-storey building with differing properties at every level, right?
Each soil layer will also have a shear capacity that must exceed the shear demands resulting from the earthquake response
In our heads, the most critical shear plans will be between soil layers, so we were wondering
1) Is it possible for a global shear/slip failure to occur between two soils in such a model? What does that look like in practice?
2) If it is possible, imagine the aforementioned stiff concrete piles going through. These piles will be subject to massively different displacement demands across the failure plane
The only way I can really see the pile surviving this is for the soil to deform around the pile...but if you're 20m below ground, will the soils be so dense that the compaction necessary to deform cannot be achieved?
If so, presumably you're pretty much guaranteed a shear failure in the pile..? Anyone have wisdom to share on this
Thanks in advance! Hopefully you guys can help settle our debate
My boss and I just went down a rabbit hole that ultimately neither of us know the answer to.
Imagine a building over deep, stiff concrete piles that transfer loads to bedrock say 25m below ground level (the numbers don't matter, this is an academic discussion primarily)
Presumably the soil layers between bedrock and ground will vary with depth, some topsoil then maybe various soft and hard sands, clays, or silts - whatever it is
The soil layers will presumably have differing mass, stiffness, and depth per layer, and so under earthquake shaking will respond uniquely to each layer
This is conceptually similar to a multi-storey building with differing properties at every level, right?
Each soil layer will also have a shear capacity that must exceed the shear demands resulting from the earthquake response
In our heads, the most critical shear plans will be between soil layers, so we were wondering
1) Is it possible for a global shear/slip failure to occur between two soils in such a model? What does that look like in practice?
2) If it is possible, imagine the aforementioned stiff concrete piles going through. These piles will be subject to massively different displacement demands across the failure plane
The only way I can really see the pile surviving this is for the soil to deform around the pile...but if you're 20m below ground, will the soils be so dense that the compaction necessary to deform cannot be achieved?
If so, presumably you're pretty much guaranteed a shear failure in the pile..? Anyone have wisdom to share on this
Thanks in advance! Hopefully you guys can help settle our debate
